Microvalve normally in a closed position

ABSTRACT

A microvalve with a normally closed state includes a membrane, an actuation means for controllable deformation of the membrane as well as a valve shutter deformable by the controllable deformation of the membrane. The valve shutter at least partially opposes the membrane and rests, in a first position in the normally closed state of the valve, along a sealing lip arranged between the valve shutter and the membrane. The sealing lip is arranged such that an outlet of the valve, which outlet is in fluid communication with an interrupted section of the sealing lip, is sealed against an input channel bordering on the valve shutter. In addition, the valve shutter is moldable into a second position so as to bring the outlet into fluidic communication with the input channel in an open state of the valve.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to components which are micromechanicallystructured, and in particular to microvalves as are used, for example,in medical engineering or in pneumatics, and to micropumps using suchmicrovalves.

2. Description of Prior Art

The growing demand for miniaturized and integrated systems has recentlyled to the development of micromechanic structural parts, such asmicrovalves and micropumps. In order to effect the necessary mechanicalactuation of such components, frequent use is made of piezoceramicswhich contract in the direction of polarization of the piezoceramic uponapplication of voltage.

To illustrate the operation of such piezoceramics, FIGS. 6 a, 6 b and 6c show the state of a piezoceramic in three different voltage drivestates. The piezoceramic 900, shown in FIGS. 6 a to 6 c, hasmetallizations 910 a and 910 b on two opposing outer surfaces ofpiezoceramic 900. Metallization 920 a and 920 b oppose each other in thedirection of the direction 920 of polarization of piezoceramic 900, thevoltage U applied to same is zero in FIG. 6 a, whereas the voltage ispositive in FIG. 6 b and negative in FIG. 6 c. As can be seen,piezoceramic 900 contracts in a direction transverse to the direction ofpolarization in the case where the voltage U applied is positive, incomparison to the case where the voltage U applied is zero. Due to theflatness of the piezoceramic, which is, for example, 5 μm, in comparisonwith an edge length of, for example, 5 mm, a contraction in thedirection of polarization is small. The application of a voltage U inthe opposite direction of the direction of polarization 920 does notlead to an expansion but to a depolarization of piezoceramic 900, as isindicated by the arrow 920 which is reversed in comparison with thearrows 920 a and 920 b shown in FIGS. 6 a and 6 b.

In order to implement the contractive effect of the piezoceramic, as isrepresented in FIGS. 6 a to 6 c, in a suitable manner, use is made, forexample, as is known, of a combination of a membrane and a piezoceramicfixed to the same, an example of a bending converter obtained from sucha combination being shown in FIGS. 7 a, 7 b and 7 c. A bending converterconsists of a piezoceramic 900 which is firmly connected, on a mainside, to a membrane 930. While FIG. 7 a represents the voltage drivestate, since the voltage applied to piezoceramic 900 is zero, FIGS. 7 band 7 c show those voltage drive states where the voltage applied topiezoceramic 900 is positive and negative, respectively. If ceramic 900contracts when a voltage which is positive along the direction ofpolarization is applied, the firm connection of piezoceramic 900 tomembrane 930 causes membrane 930 to bend, as is shown by arrows 940 inFIG. 7 b. Consequently the contraction of piezoceramic 900 is convertedto a stroke of membrane 930 in a direction 940 away from piezoceramic900 when a positive voltage is applied to piezoceramic 900. Even thoughan expansion of piezoceramic 900 and, as a consequence, bending ofmembrane 930 in the opposite direction should be expected when aninverse voltage, i.e. a voltage which is negative in the direction ofpolarization, is applied, this voltage drive is small and cannot beutilized in a technical manner since it would lead to a depolarizationof piezoceramic 900, this being illustrated by the fact that FIG. 7 c iscrossed out.

Even though the bending converter described with reference to FIGS. 7 ato 7 c is fast, exhibits low energy consumption, large/high stroke and astrong force, and, in addition, has the advantage, in particular withregard to employment in microfluidics, that it causes the medium to beswitched to be separated from the piezoceramic, a drawback of this typeof bending converter is that it can only carry out an active movement inthe direction of the membrane (downward in FIGS. 7 a to 7 c) due to theunsymmetrical nature of the piezoeffect as has been described withreference to FIGS. 6 a to 6 c. An inverse movement (upward) can only berealized by the bending converter if a voltage is applied in theopposite direction of the direction of polarization, which, however,leads to a depolarization of the piezoceramic even at minor fieldstrengths in the opposite direction. Typical depolarization fieldstrengths of piezoceramics are roughly −4000 V/cm.

A known microvalve uses the bending converter described above so as torealize a valve function wherein the valve is normally open. Such aknown normally-open microvalve (in the following referred to as NOvalve) is shown in FIGS. 8 a and 8 b, FIG. 8 a representing the closedstate of the valve and FIG. 8 b representing the normally-open state ofthe valve. As is shown in FIGS. 8 a and 8 b, such a conventional NOvalve includes a bending converter such as has been described above,which consists of a piezoceramic 900 and a membrane 930, as well as avalve seat arranged below membrane 930 and comprised of a sealing lip960 which surrounds an opening 970. As is shown in FIG. 8 b, in thenormally-open case, i.e. if no voltage is applied to the piezoceramic,membrane 930 is spaced apart from sealing lip 960 so that, as is shownby an arrow 980 in FIG. 8 b, a fluid may penetrate through opening 970.If a positive voltage is applied to piezoceramic 900, membrane 930moves, due to the bending as has been explained with reference to FIGS.7 a to 7 c, in the direction of sealing lip 960, with the membrane 930resting, in the fully closed position, on sealing lip 960 so as to closeopening 970.

One drawback of the NO valve described above is that, if the voltageapplied to the piezoceramic is switched off or interrupted, the membranereturns to its resting position where it is spaced apart from the valveseat, whereby the valve enters into an open state. However, many areasof application, such as medicine, require valves which are closed intheir normal state. In drug administration, it must be ensured, forexample, that no drug is administered to the patient in the case of apower failure, so as to avoid that the patient is administered anoverdose. To prevent this, a “normally closed” function is required.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a microvalve with anormally closed state.

In accordance with an aspect of the present invention this is achievedby an inventive microvalve with a normally closed state comprising amembrane, an actuation means for controllable deformation of themembrane as well as a valve shutter which is deformable by thecontrollable deformation of the membrane. The valve shutter at leastpartially opposes the membrane and rests, in a first position in thenormally closed state of the valve, along a sealing lip arranged betweenthe valve shutter and the membrane. The sealing lip is arranged suchthat an outlet of the valve, which outlet is in fluidic communicationwith an interrupted section of the sealing lip, is sealed in afluidtight manner against an input channel bordering on the valveshutter. In addition, the valve shutter is deformable into a secondposition so as to bring the outlet into fluidic communication with theinput channel in an open state of the valve.

The present invention is based on the observation that the inputpressure exerted on the valve by the fluid to be switched can be usedfor pressing a valve shutter, such as a flap, against sealing lips so asto close the valve. For opening the valve, merely an actuation means isrequired which shifts the valve shutter from the closed position to theopen position. In this way it is ensured that the valve remains closedin case of a power failure or other incidents.

In accordance with one embodiment the valve shutter may be a shutterflap engaged near the interrupted section of the sealing lip, thedeformation of the valve shutter corresponding to a flap-like bending ofthe shutter flap. Opening the shutter flap creates a gap through whichthe fluid to be switched may flow.

The valve shutter, such as, for example, the shutter flap, may be formedso as to be thicker in one or several places, may be stiffened or mayexhibit ribs so as to prevent, on the one hand, bending of the shutterflap in non-engaged, undesired places in the open state of the valve,which would otherwise lead to an undesired closing of the shutter flapdue to the inlet pressure, and so as to avoid, on the other hand,bending of the shutter flap due to the inlet pressure in the normallyclosed state of the valve, which bending might otherwise cause theshutter flap to rest, in an oblique manner, along the sealing lip sothat poor sealing is achieved. In order to further reduce bending of thevalve shutter in the normally closed state of the valve, supportingelements may be provided in suitable places between the membrane and thevalve shutter which prevent the valve shutter from bending.

In accordance with a further embodiment the valve shutter is a bendablemembrane engaged at two opposing edge portions. If the bendable membranebends due to a deformation of the membrane, two opposing gaps resultthrough which a medium to be switched may flow to the outlet.

On one side of the membrane which opposes the valve shutter, a tappetmay be provided. This yields the advantage, on the one hand, that lessdeformation and/or less stroke is required to press open the valveshutter, and, on the other hand, that the flow resistance of thepenetrating fluid may be reduced during the open state of the valvesince the distance between the membrane and the shutter flap can beselected freely by means of the height of the tappet and does not dependon the maximum stroke and/or the maximum deformation of the membrane.

The sealing lip may be guided in a meander-like or in another fashion soas to increase the length of the sealing lip at which the fluid may passin the open state of the valve. This is advantageous particularly inpneumatics since higher throughput rates may thereby be achieved.

In accordance with a specific embodiment the NC valve, or the normallyclosed valve, consists of a first chip and a second chip. The first chipincludes the membrane, on which the tappet and a piezoceramic as anactuation means are mounted on opposing sides, and the sealing lip,which surrounds the rectangular membrane along three sides. The secondchip includes the shutter flap as the valve shutter, the shutter flapbeing fixed near that side of the membrane on which the sealing lip isinterrupted and does not surround the membrane.

The first chip and the second chip are bonded such that the shutter flapat least partially opposes the membrane and that the shutter flap ishigher than the sealing lip. An advantage of this arrangement is that abonding step that does not make use of a joining layer may be used forconnecting the two chips, so that no space results between the tappet120 and the shutter flap 180, so that the reproducibility of the valveis increased due to the non-occurrence of variations in the thickness ofadhesive, and that, in addition, media resistance and tolerance isimproved. Furthermore, a valve thus formed may easily be integrated intoa microfluid system formed from a chip, whereby a microfluid systemhaving a smaller dead volume and thus shorter switching times may beobtained, which is advantageous particularly in pneumatics.

One advantage of the inventive valve is that it exhibits a normallyclosed state, so that it is closed even if power supply fails or isinterrupted in any other way. Another advantage is that the inventivevalve can be easily integrated in existing microsystems.

A further advantage of the present invention is that, due to the factthat the circumference of the valve shutter is freely selectable and canbe designed to be large, higher throughput rates may be achieved thanwith conventional valves, in which merely one small opening is pressedshut by an active element.

Due to the provision of a membrane for separating the actor from thefluid to be switched, the inventive valve is suitable, as opposed tovalves which, for example, use electrostatic attraction as the switchingforce, both for liquids and gases or mixtures of same, whereby the rangeof application of the valve is increased.

In accordance with one embodiment the inventive NC valve is connectedupstream from a micromembrane pump, the micromembrane pump and the NCvalve being mounted on a carrier substrate comprising connectingchannels which connect same.

In accordance with a further embodiment a microperistaltic pump isformed from to inventive NC valves which are connected with each othervia a pumping chamber having a pumping membrane and are arranged back toback. The peristaltic pump thus obtained may be realized in a one-chipsolution and is moreover self-locking in both directions even if novoltage is applied.

A further embodiment provides a 3/2-way microvalve on a chip, aninventive NC valve and a conventional NO valve being used for this.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the accompanying drawings, preferred embodiments ofthe present invention will be described in more detail below, wherein

FIGS. 1 a and 1 b show side sectional views of an embodiment of an NCvalve in accordance with the present invention, FIG. 1 a representingthe normally closed state of the valve and FIG. 1 b representing theopen state of the valve;

FIGS. 2 a and 2 b show a bottom view of an actor chip and a top view ofa flap chip, respectively, of the NC valve of FIGS. 1 a and 1 b in thenormally closed state of the valve;

FIG. 3 shows a side sectional view of an embodiment wherein the NC valveof FIGS. 1 a, 1 b, 2 a and 2 b is connected upstream from amicromembrane pump;

FIG. 4 shows a side sectional view of an embodiment of a peristalticpump consisting of two NC valves arranged back to back which correspondto that shown in FIGS. 1 a, 1 b, 2 a and 2 b;

FIGS. 5 a and 5 b show a side sectional view of an embodiment of a3/2-way valve comprising the NC valve shown in FIGS. 1 a, 1 b, 2 a and 2b, FIGS. 5 a and 5 b showing different voltage drive states;

FIGS. 6 a, 6 b and 6 c show diagrams illustrating the voltage drive of apiezoceramic, the voltage applied to the piezoceramic in the directionof polarization is zero in FIG. 6 a, is positive in FIG. 6 b and isnegative in FIG. 6 c;

FIGS. 7 a, 7 b and 7 c show diagrams illustrating the movement of amembrane of a bending converter with a piezoceramic at different voltagedrive states, the voltage applied to the piezoceramic in the directionof polarization being zero in FIG. 7 a, positive in FIG. 7 b andnegative in FIG. 7 c; and

FIGS. 8 a and 8 b show a side sectional view of a conventional NO valve,FIG. 8 a representing the closed state of the valve and FIG. 8 brepresenting the normally-open state of the valve.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Before various embodiments of the present invention will be describedwith reference to the figures, it shall be pointed out that likeelements in the various figures have been provided with like referencenumerals and that a repeated explanation of identical elements will beomitted in the description of the figures so as to avoid repetitions inthe description.

With reference to FIGS. 1 a, 1 b, 2 a and 2 b, an embodiment of an NCvalve in accordance with the present invention will initially bedescribed, wherein FIGS. 1 a and 1 b show side sectional views of thevalve in a normally closed state and an open state, respectively, of thevalve, and FIGS. 2 a and 2 b show a bottom view of an actor chip and atop view of a flap chip, respectively, of the valve in the normallyclosed state of the valve. It shall be pointed out that FIGS. 1 a, 1 b,2 a and 2 b show the structures, by way of example, with slopes such asoccur in KOH etching, it being possible, however, to produce thestructures shown in another manner without slopes.

As can best be seen in FIGS. 1 a and 1 b, the NC valve 10 consists of afirst chip, or an actor chip, 20 as well as a second chip, or a flapchip, 30. Actor chip 20 comprises a dip or recess 50 on a first mainside 40 and a dip 70 on an opposing main side 60, a membrane 80, whichwill be referred to as actor membrane hereinafter, being formed throughboth dips 50 and 70. A piezoceramic 100 is arranged on a first side 90of the actor membrane, while a tappet 120 protrudes on a second side 110of actor membrane 80.

FIG. 2 a shows tappet 120, dip 70 and, by means of the dashed line, thearea of the dip which forms actor membrane 80, seen from main side 60 ofactor chip 20, wherein actor membrane 80 and tappet 120 are formedessentially squareshaped in the lateral direction and further arearranged in a centered arrangement. It can further be seen that membrane80 is surrounded by a sealing lip 130 along three of its four sides oredge sections. As can best be seen in FIGS. 1 a and 1 b, sealing lip 130is arranged on main side 60 of actor chip 20—main side 60 beingstructured, for example, simultaneously with tappet 120—so as toprotrude there, and exhibits a cross-section which correspondsessentially to a triangle with a flattened tip.

Flap chip 30 is connected to actor chip 20 and includes an outlet regionor an outlet port 140 which forms a passageway extending from a firstmain side 150 to a second main side 160 of flap chip 30, as well as aninput channel region 170 formed by a dip in the second main side 160which extends to a shutter flap or a flap membrane 180. As is shown inFIG. 2 b, the shutter flap is formed in a square shape, any other formbeing also possible, however, and is freely movable, via a slot 185, onthree of its four side or edges, relative to the rest of flap chip 30,the shutter flap being fixed to or engaged on the fourth side. Valveflap 180 extends somewhat beyond the lateral extension of sealing lip130 along its lateral extension so that in the normally closed state ofvalve 10, input channel region 170 is limited laterally by flap chip 30,and is limited against outlet region 140 by valve flap 180, sealing lip130 and a part 70 b of dip 70, wherein part 70 b surrounds sealing lip130. It must be noted that the shape of input channel region 170 is alsoessentially square in this embodiment in the lateral direction, i.e.parallel to the drawing plane of FIGS. 2 a and 2 b, even though thiscannot be seen in FIGS. 2 a and 2 b, it also being possible to use othershapes.

It shall be pointed out that a bending converter is realized, bypiezoceramic 100 and actor membrane 80, the operation of which has beendescribed with reference to FIGS. 6 a to 6 c and 7 a to 7 c. Inparticular, in the embodiment shown, the bending converter consists of apiezoceramic 100 on which metallizations are formed on sides opposingeach other in the direction of the direction of polarization, and whichexhibits a high d31 or charge coefficient. Membrane 80 consists ofsilicon, but other materials are also possible. However, piezoceramic100 is mounted to silicon membrane 80 by means of a suitable adhesive.The silicon piezoelectric bending converter thus formed is adapted suchthat actor membrane 80 is still able, at an applied voltage swing at aspecified counterpressure, to become deflected by a distance, or stroke,which is also specified. In this silicon bending converter, typicalvalues are 1 to 10 bar for the counterpressure, 5 to 40 μm for thestroke, 4 to 15 mm for the side length of the actor membrane and 1 msfor the switching time.

One possible method of manufacturing the NC valve described above willbe described briefly below. At first, actor chip 20 and flap chip 30undergo an etching process, such as, for example, anisotropic KOHetching, so as to form dip 50, dip 70, membrane 80, tappet 120 andsealing lip 130, and/or to form outlet region 140, input channel region170 as well as shutter flap 180. Then, both chips 20 and 30 are bondedwith each other in a wafer-bonding step that does not make use of ajoining layer, such as the silicon fusion wafer bond. After thewafer-bonding step, tappet 120 firmly adheres to shutter flap 180, andthe edge of shutter flap 180 firmly adheres to sealing lip 130. The edgeof the flap is released again from the sealing lip by etching fromprinciple side 160 of flap chip 30. The etching time may either beselected to be long enough that, in addition to the sealing lip, thetappet is also released from the shutter flap, or the etching time isselected to be shorter so as to release only the sealing lip, and notthe tappet, from the shutter flap. For this purpose, the thickness of anoxide layer applied onto principle side 60 before the waferbonding stepis preferably selected such that places that are to be etched free afterwafer-bonding can be etched free by lateral underetching. Principle side40 of actor chip 20 may be coated with aluminum, for example, so as toserve as a contact for piezoceramic 100.

The operation of the NC valve of FIGS. 1 a, 1 b, 2 a and 2 b will beexplained below. As can be seen in FIG. 1 a, the shutter flap isarranged such that the lateral dimensions of shutter flap 180 are largerthan circumferential sealing lip 130 of actor chip 20, and that theinlet pressure, applied to shutter flap 180 bordering on input channelregion 170 in the input channel region 170 by a fluid to be switched,has a closing effect. Without application of voltage to piezoceramic 100and, thus, without any application of pressure to shutter flap 180,shutter flap 180 is therefore closed. For opening valve 10 a voltagewhich is positive in the direction of polarization is applied to thesilicon piezoelectric bending converter formed by piezoceramic 100 andmembrane 80, whereby the silicon piezoelectric bending converter pressesopen sealing flap 180 against the inlet pressure using tappet 120. To beprecise, the positive voltage applied to piezoceramic 100 in thedirection of polarization causes membrane 80 to be moved, along withtappet 120, in the direction of valve flap 180, which bends open due tothe pressure of tappet 120 and forms a gap 190 between itself andsealing lip 130, as can be seen in FIG. 1 b.

It shall be pointed out that gap 190 arises along the three freelymovable edge sections of valve flap 180, and that therefore any fluidthat may be present in input channel region 170 may flow around threeedges of valve flap 180 so as to reach outlet region 140, even thoughthis cannot be seen in FIG. 1 b which shows merely a side sectionalview. In order to prevent the valve flap from being bent toward sealinglip 130 due to the inlet pressure and to the relatively strong leveringeffect at the freely movable edge sections of valve flap 180, it may beadvantageous to design the thickness of the shutter flap such that theshutter flap can be very easily bent near the engagement location, andthat the shutter flap is reinforced in particular in the area opposingthe engagement location via tappet 120 and does not bend there at all,if possible. In this way one prevents, for example, that valve flap 180does not bend back to sealing lip 130 in the picture of FIG. 1 b, whichprevents gap 190 from narrowing or even closing along the edge, of valveflap 180, opposing the engagement location, in the open state of valve10. The stiffening of valve flap 180, by which same is formed to bethicker in certain places, can further be used to prevent, in thenormally closed state of valve 10, shutter flap 180 from bending due tothe inlet pressure, whereby the leaking rate of the valve can be reducedsince shutter flap 180 also rests upon the corners of sealing lip 130.

Further it is to be noted that the height of tappet 120 and/or the depthof dip 70 is selected such that the flow resistance of the fluid to beswitched through gap 190, which is about to form, and the space betweenactor membrane 80 and shutter flap 180, remains low in the open state ofvalve 10. The depth of dip 70 is, for example, 100 to 300 μm.

Even though it is not shown in FIGS. 1 a, 1 b, 2 a and 2 b, supportingelements may be provided between actor membrane 80 and shutter flap 180in suitable places, such as, for example, near right-hand corners, asseen from the observer's perspective, which supporting elements maypreferably be provided on actor membrane 80 or on shutter flap 180.These supporting elements prevent shutter flap 80 from bending in theregion between tappet 120 and sealing lip 130 in the normally closedstate of NC valve 10, and therefore prevent shutter flap 180 fromresting on sealing lip 130 in an oblique manner. In this way, the sealin the normally closed state of valve 10 can be improved. If thesupporting elements are provided on actor membrane 80, they preferablyhave a very narrow cross-section so as not to affect the bendingproperties of actor membrane 80, and they are preferably formed in thesame etching steps as tappet 120 and sealing lip 130, and are releasedfrom shutter flap 180 after bonding.

With reference to FIGS. 3 to 5 a and 5 b, embodiments shall be describedbelow wherein the NC valve described with reference to FIGS. 1 a, 1 b, 2a and 2 b is used.

FIG. 3 shows a hybrid combination of the NC valve 10 having amicromembrane pump, the micromembrane pump 300, which comprises twopassive non-return valves 302 a and 302 b aligned in opposing directionsand a pumping chamber 304, and the NC valve being arranged on a carriersubstrate 310 having channels 320 a, 320 b and 320 c formed therein. Inparticular, the connecting channel 320 a is connected to input channelregion 170 of NC valve 10, whereas connecting channel 320 b bringsoutlet region 140 into fluidic communication with an input 330 ofmicromembrane pump 300. Connecting channel 320 is connected to theoutput 340 of micromembrane pump 300.

An arrangement is achieved which is self-locking in both flow directionswithout any voltage applied, due to the operation of NC valve 10. Inthis way, the arrangement is suitable as a self-locking micropump formedical engineering. A further advantage of using the NC valve in thisarrangement is that high flow rates can be achieved in that NC valve 10is optimized toward a low flow resistance, in that, as has beenmentioned above, the height of the tappet is suitably adjusted, and inthat the micromembrane pump is designed with a view to a highthroughput.

FIG. 4 shows an embodiment of a peristaltic pump wherein two NC valves10 a and 10 b, arranged back to back, are used which correspond to thatdescribed with reference to FIGS. 1 a, 1 b, 2 a and 2 b, with theexceptions to be described hereinbelow. As can be seen in FIG. 4, bothactor chips and both flap chips of NC valves 10 a and 10 b areintegrated into a single chip 400 and 410, respectively. Both outletregions of NC valves 10 a and 10 b have been replaced by a pumpingchamber 420 extending between both chips 400 and 410 and connecting theregions located between actor membrane 80 a and 80 b and valve flaps 180a and 180 b of valve 10 a and of valve 10 b. Above pumping chamber 420,chip 400 exhibits a dip 430, whereby a pumping membrane 440 is formed.On that side of pumping membrane 440 which is facing away from pumpingchamber 420, a piezoceramic 450 is mounted. The voltages applied topiezoceramics 100 a and 100 b of both NC valves 10 a and 10 b as well asto piezoceramic 450 are driven in a suitable manner so as to achieve apumping action from a gate 460, formed by the input channel region of NCvalve 10 a, to a gate 470, formed by the input channel region of NCvalve 10 b, or vice versa.

The architecture of a peristaltic pump, as has been described withreference to FIG. 4 by means of two NC valves, as have been describedwith reference to FIGS. 1 a, 1 b, 2 a and 2 b, is advantageous in thatthe peristaltic pump is self-locking in both directions even in ade-energized state, i.e. even in the case of a voltage breakdown. Inaddition, the peristaltic pump can be realized in a one-chip solution.

However, it shall be pointed out that the dip depth of NC valves 10 aand 10 b is preferably only 10 to 50 μm in the present case, contrary tothe above description, so as to achieve a high compression ratio(compression ratio=stroke volume of the pumping membrane/dead volume ofthe pumping chamber) and therefore a desirably high tolerance of thepump with respect to bubbles. Due to the gap flows occurring as aconsequence, limited flow rates of the pump must be expected. The choiceof the dip depth therefore represents a compromise between the highestpossible flow rate and the highest possible tolerance toward bubbles.

It shall be pointed out, with reference to FIG. 4, that it is furtherpossible to construct a peristaltic pump which uses only an NC valvecorresponding to that shown in FIGS. 1 a, 1 b, 2 a and 2 b, and whichuses, as a second valve, a valve shown, for example, in FIG. 8.

An embodiment of a 3/2-way microvalve will be described with referenceto FIGS. 5 a and 5 b, FIGS. 5 a and 5 b showing side sectional views ofsame in different voltage drive states. The 3/2-way microvalve consistsof an NC valve 10 such as that shown in FIGS. 1 a, 1 b, 2 a and 2 b, andof an NO valve 500, both valves being realized on one chip. Inparticular, a chip 510 includes the actor chip of NC valve 10 as well asa further dip 520 through which a membrane 530 is formed on which apiezoceramic 540 is mounted. A second chip 520 bonded to the first chipincludes, in addition to the flap chip of NC valve 10, an outlet region550 which extends from a main side of chip 520, which side is facingfirst chip 510, to that main side of chip 520 which is facing first chip510, and ends there at an opening 555 surrounded by a sealing lip 557.The architecture of NO valve 500, which consists of a bending converterformed by membrane 530 and piezoceramic 540, and a valve seat which isformed by sealing lip 557 surrounding opening 555, corresponds to theconventional NO valve described with reference to FIGS. 8 a and 8 b withregard to its mode of operation.

In the 3/2-way valve described above, the input channel region of NCvalve 10 serves as an input 560 of the 3/2-way valve, whereas outletregion 550 of NO valve 500 serves as a first output, and the outletregion of NC valve 10 serves as a second output 570. Input 560 or theinput channel region of NC valve 10 is in fluidic communication with theregion located between membrane 530 and sealing lip 557 of NO valve 500,so that NC valve 10 is connected between input 560 and output 570, andNO valve 500 is connected between input 560 and output 550.

The voltages applied to piezoceramic 100 of NC valve 10 and topiezoceramic 540 of NO valve 500 are driven in a suitable manner so asto produce a valve action between input 560 and the first output 550 andbetween input 560 and the second output 570. For the purpose ofillustrating the mode of operation of the 3/2-way valve, two differentvoltage drive states are shown in FIGS. 5 a and 5 b for piezoceramics100 and 540 of NC valve 10 and of NO valve 500. If a voltage which ispositive in the direction of polarization is applied to piezoceramics100 and 540 of both valves 10 and 500, NC valve 10 is open, whereas NOvalve 500 is closed, as can be seen in FIG. 5 a. In the normal state,i.e. when no voltage is applied, the NC valve is in its normally closednormal state, whereas NO valve 500 is in an open state.

Using NC valve 10 between input 560 and output 570 of the 3/2-way valvecan prevent that, in case of a voltage breakdown, a fluid to be switchedpasses from input 560 to the second output 570, but it is achieved thatsame can flow merely from input 560 to output 550, as can be seen inFIG. 5 b.

It shall be pointed out, with reference to FIGS. 4, 5 a and 5 b, thatthe inventive valve or a plurality of same may be combined at randomwith other microfluid devices, such as, for example, pumps, valves, soas to form a microfluid system. The microfluid system thus produced mayfurther be realized in a chip, whereby increased switching times can berealized. A valve having an input and two outputs and being self-lockingwithout voltage might be formed, for example, from a NO valve and an NCvalve, the input channel region of the NC valve serving as the input,the outlet region of the NC valve serving as a first output, and theoutlet region of the NO valve serving as a second output, the regionbetween the bending converter and the valve seat of the NO valve beingconnected with the region located between the actor membrane and theshutter flap of the NC valve.

Even though in the preceding embodiments the microvalve consisted of twosilicon chips and/or isolated silicon wafers, which were bondedtogether, as the substrates, it shall be pointed out that the microvalvemay further be formed differently, such as, for example, by depositingseveral photolithographically structured layers and etching cavities tobe formed. Moreover, the microvalve is not limited to certain materials.In addition to the semiconductor materials described above, the NC valveused may further consist of plastic or other materials suitable formicrofluidics.

Even though in the above a bending converter consisting of the actormembrane and the piezoceramic as an actuation means has been used as anactuation means, it is further possible to provide other actuationmeans. The actuation means might consist, for example, of a piezo stackor of a heating resistor expanding upon an increase in temperature. Inthis case, the main side, opposing the valve flap, of the actor membranewould oppose a supporting structure between which the heating resistoris arranged. Another possibility would be to apply a pressure to thatmain side of the actor membrane which is facing away from the valveflap, if the microvalve is to be opened. In this case, the actuationmeans would consist of one element producing overpressure.

With regard to the tappet described above, it shall be pointed out thatsame is not absolutely necessary for the operation of the presentinvention. However, the presence of the tappet is advantageous forreducing the stroke of the actor membrane required to open the valveflap. If a tappet is used, same may exhibit any lateral form, eventhough it is advantageously limited, in the lateral direction, to aregion in the center of the actor membrane, so as not to degrade thebending properties of the actor membrane and so as to be located in theregion of the actor membrane with the maximum stroke. It is further notessential whether or not the tappet contacts the valve flap in thenormally closed state. In addition, it is possible that the tappeteither only contacts the valve flap or is connected to the same. It isfurther possible to provide the tappet on the valve flap so that thetappet extends from the surface of the valve flap in the direction ofthe actor membrane.

The following shall be pointed out with regard to the sealing lip. Eventhough the sealing lip exhibited an essentially triangular cross-sectionabove, it is further possible that same exhibits other cross-sections.Even though it has been described above that the sealing lip surroundsthe actor membrane, it is further possible that the sealing lip isprovided on the actor membrane; in this case one should make sure thatsuch an arrangement does not deteriorate the bending properties of theactor membrane too much. For the sealing lip it is merely essential thatsame seals any passageway from the input channel region to the outletregion in the normally closed state of the microvalve. Therefore, thesealing lip might further be arranged such that same does not surroundthe tappet. In this case the valve flap would be provided such that sameexhibits a region extending laterally beyond the extension of thesealing lip so as to seal the input channel region against the outletregion in the normally closed state, and a region upon which themembrane and/or the tappet can act in order to open the valve flap. Itshall further be pointed out that the sealing lip might also be arrangedon the valve flap, even though provision of the valve flap on the actorchip is preferred so as to prevent too much stiffening of the valveflap.

In accordance with a further embodiment the sealing lip is not guided ina straight line as in FIGS. 2 a and 2 b, but is guided in a differentmanner, such as, for example, meander-like or wave-like, so as toincrease the length of the sealing lip where the gap between the actormembrane and the valve flap forms. In this way a considerable increasein the throughput rate may be achieved by a slight enlargement of thevalve flap, which provides advantages particularly in pneumatics.

Even though embodiments have been described above wherein a valve flapis used as the valve shutter, other valve shutters may further be usedwhich may be deformed by the controllable deformation of the actormembrane. For example, a membrane engaged on two sides may be usedinstead of a valve flap engaged on one side. In this case, the inputchannel region will be connected with the outlet region, in the openstate of the valve, merely via two opposing gaps between two sealinglips and the membrane acting as the valve shutter. In this case, thesealing lip could not be seen in FIGS. 1 a and 1 b, but the shutter flapalong this edge would also be fixed to the flap chip instead. In theopen state, the valve shutter membrane would bend in the form of acylinder segment with a curvature along the direction between the twoedges engaged, so that a gap is formed between the sealing lip and thevalve shutter membrane so as to form a passageway, at both otheropposing edges of the valve shutter membrane, i.e. upstream anddownstream from the drawing plan of FIGS. 1 a and 1 b. In a similarmanner, a valve shutter which is engaged on three sides might beprovided, the deformability being reduced, however.

It shall be pointed out, with reference to FIGS. 3, 4, 5 a and 5 b, thatthe embodiments shown in them show merely specific possibilities ofapplying the inventive NC microvalve and that other examples ofapplication are also possible.

1. A microvalve with a normally closed state, comprising a membrane; anactuation means for controllable deformation of the membrane; a valveshutter which is deformable by the controllable deformation of themembrane, which at least partially opposes the membrane, and whichrests, in a first position in the normally closed state of the valve,along a sealing lip arranged between the valve shutter and the membrane,the sealing lip being arranged such that an outlet of the valve, whichoutlet is in fluidic communication with an interrupted section of thesealing lip, is sealed in a fluid-tight manner against an input channelbordering on the valve shutter, and the valve shutter being deformableinto a second position so as to bring the outlet into fluidiccommunication with the input channel in an open state of the valve. 2.The microvalve as claimed in claim 1, wherein, on one side of themembrane, which side is opposite to the valve shutter, a tappetprotrudes for pressing against the valve shutter, when the actuationmeans deforms the membrane.
 3. The microvalve as claimed in claim 1,wherein the actuation means is a piezoceramic arranged on a side of themembrane which is facing away from the valve shutter.
 4. The microvalveas claimed in claim 1, wherein the valve shutter is a shutter flapengaged near the interrupted section of the sealing lip, and wherein thedeformation of the valve shutter is a flapping bending of the shutterflap.
 5. The microvalve as claimed in claim 4, wherein the shutter flapis stiffened at one or several parts of the non-engaged locations. 6.The microvalve as claimed in claim 1, wherein the valve shutter is abendable membrane engaged at two opposing edge sections, one of the edgesections being located near the interrupted section of the sealing lip,and wherein the deformation of the valve shutter is a bending of thebendable membrane.
 7. The microvalve as claimed in claim 1, wherein themembrane and the sealing lip are structured into a substrate, andwherein a gap is formed between the sealing lip and the valve shutterdue to the deformation of the valve shutter, by which gap the outlet isin fluid communication with the input channel.
 8. The microvalve asclaimed in claim 2, wherein the sealing lip surrounds the tappet exceptfor the interrupted section.
 9. The microvalve as claimed in claim 1,further comprising: a first chip in which the membrane which issurrounded by the sealing lip along the edge of the membrane except foran interrupted section, is formed, and a second chip which is bonded tothe first chip and in which the valve shutter is formed, wherein thelateral extension of the valve shutter (180) exceeds at least thelateral extension of the sealing lip, and wherein the valve shutter isconnected to the second chip at least near the interrupted section. 10.The microvalve as claimed in claim 9, wherein a tappet bonded to thevalve shutter is formed on the membrane.
 11. The microvalve as claimedin claim 1, wherein supporting elements are formed between the valveshutter and the membrane so as to prevent, in the normally closed stateof the valve, an undesired partial bending of the valve shutter.
 12. Amicroperistaltic pump comprising at least one microvalve with a normallyclosed state, said microvalve comprising a membrane (80); an actuationmeans (100) for controllable deformation of the membrane (80); a valveshutter (180) which is deformable by the controllable deformation of themembrane (80), which at least partially opposes the membrane (80), andwhich rests, in a first position in the normally closed state of thevalve, along a sealing lip (130) arranged between the valve shutter(180) and the membrane (80), the sealing lip (130) being arranged suchthat an outlet (140) of the valve, which outlet is in fluidiccommunication with an interrupted section of the sealing lip (130), issealed in a fluid-tight manner against an input channel (170) borderingon the valve shutter (180), and the valve shutter (180) being deformableinto a second position so as to bring the outlet (140) into fluidiccommunication with the input channel (170) in an open state of thevalve.
 13. A three/two-way microvalve comprising at least one microvalvewith a normally closed state, said microvalve comprising a membrane(80); an actuation means (100) for controllable deformation of themembrane (80); a valve shutter (180) which is deformable by thecontrollable deformation of the membrane (80), which at least partiallyopposes the membrane (80), and which rests, in a first position in thenormally closed state of the valve, along a sealing lip (130) arrangedbetween the valve shutter (180) and the membrane (80), the sealing lip(130) being arranged such that an outlet (140) of the valve, whichoutlet is in fluidic communication with an interrupted section of thesealing lip (130), is sealed in a fluid-tight manner against an inputchannel (170) bordering on the valve shutter (180), and the valveshutter (180) being deformable into a second position so as to bring theoutlet (140) into fluidic communication with the input channel (170) inan open state of the valve.
 14. A microfluid system comprising at leastone microvalve with a normally closed state, said microvalve comprisinga membrane (80); an actuation means (100) for controllable deformationof the membrane (80); a valve shutter (180) which is deformable by thecontrollable deformation of the membrane (80), which at least partiallyopposes the membrane (80), and which rests, in a first position in thenormally closed state of the valve, along a sealing lip (130) arrangedbetween the valve shutter (180) and the membrane (80), the sealing lip(130) being arranged such that an outlet (140) of the valve, whichoutlet is in fluidic communication with an interrupted section of thesealing lip (130), is sealed in a fluid-tight manner against an inputchannel (170) bordering on the valve shutter (180), and the valveshutter (180) being deformable into a second position so as to bring theoutlet (140) into fluidic communication with the input channel (170) inan open state of the valve.